It's an Emoto Eco 2.5. You're lucky because it has standard parts, unlike the other models. You don't need a conversion kit for it because the motor will be fine. If you get a 36v battery for it and a 36v modern controller, it will be completely transformed.
The battery is a standard Silver Fish battery that you can buy pretty cheaply on Ebay for £150 to £250, depending on capacity and quality. A controller will cost from £40 to £70, though I'd recommend the £70 one because you'd have a lot more power, which is more controllable and adjustable with that one.
Is your back brake a disc or a band-brake?